Variable displacement hydraulic apparatus



May 25, 1965 w. w. HEADINGs ETAL 3,185,1:05

VRIABLE DISPLACEMENT HYDRAULIC APPARATUS 3 Sheets-Sheet l E Filed March 30, 1959 May 25, 1965 w. w. HEADINGs ETAL 3,185,105

VARIABLE DISPLACEMENT HYDRAULIC APPARATUS Filed March 30, 1959 3 Sheets-Sheet 2 xxx mxx NNN hxx

w. w. HEADINGS ETAL 3,185,105 VARIABLE DISPLACEMENT HYDRAULIC APPARATUS Filed March 30, 1959 5 Sheets-Sheet 3 May 25, 1965l f 71. z/enorsf ZQZZ'ZzZzm ZU. brenda' 011 f?? United States YPatent O 3,185,165 VARIABLE DEPLACEMENT HYDRAULC APPARATUS William W. Headings, Willoughby, and Howard E. Rose,

Hudson, hio, assignors to Borg-Warner Corporation,

Chicago, Ill., a corporation of illinois Filed Mar. 3l), 1959, Ser. No. 802,82i 2 Claims. (Cl. 163-162) This invention relates to a variable displacement hydraulic apparatus, and, in particular, relates to a piston type pump or motor having means to vary the amount of tluid displaced by the pump.

The conventional piston type pump or motor comprises a housing having a cavity formed therein. A block is rotatably supported in the cavity and is provided with a plurality of cylinders passing therethrough and being disposed in circular array around the axis of rotation of the block. A rotatable member, having an axis of rotation disposed angularly with respect to the axis of rotation of the block, is rotatably supported within the cavity of the housing and is operatively interconnected with the cylinder block. The rotatable member carries a plurality of pistons having portions thereof disposed respectively in the cylinders formed in the block. Since the axis of rotation of the rotatable member is disposed angularly with respect to the axis of rotation of the block, rotation of the rotatable member effects rotation of the cylinder block and reciprocative movement of each piston Within its respective cylinder when the hydraulic apparatus is acting as a fluid pump. Conversely, when the hydraulic apparatus is operating as a hydraulic motor, the pistons are reciprocated within their respective cylinders by fluid pressure and thereby cause rotation of the rotatable member, the rotatable member, in turn, eiecting rotation of the cylinder block interconnected therewith.

When the pistons are reciprocated through the angular relation of the rotatable member and block, each piston reaches its bottom dead center position when the respective piston has moved its maximum distance in one direction within the respective cylinder and further movement thereof will be in the opposite direction. Similarly, each piston reaches its top dead center position when the respective piston has moved its maximum distance iu the other direction within the respective cylinder and further movement thereof will be in the opposite direction.

When the hydraulic apparatus is operating as a hydraulic pumpp ea'ch piston, when being reciprocated within its respective cylinder from its bottom dead center position to its top dead center position by the rotational movement of the rotatable member, is adapted to draw uid through an inlet formed in the housing into the respective cylinder. As each piston is reciprocated from its top dead center position back to its bottom dead center position, the respective piston acts against the Huid previously drawn within the respective cylinder and forces the same out through an outlet formed in the housing. Similarly, when the hydraulic apparatus is operating as a hydraulic motor, pressure fluid delivered through the inlet to each cylinder acts against the end of the respective piston and causes the same to move from its bottom dead center position to its top dead center position thereby effecting rotational movement of the rotatable member. Since the rotatable member is interconnected with the rotatable block, the rotatable member causes rotation of the block and causes each piston to move from its top dead center position back to its bottom dead center position to thereby expel the fluid previously received within the respective cylinder out through the outlet.

Movement of each piston from its bottom dead cen- ICC ter position to its top dead center position is generally referred to as the intake stroke of the piston regardless of whether the hydraulic apparatus is being utilized as a hydraulic pump or motor. Similarly, the movement of each piston from its top dead center position to its bottom dead center position is referred to as the discharge stroke of the piston regardless of whether the hydraulic apparatus is being utilized as a hydraulic pump or motor.

In order to interconnect the inlet with the cylinders wherein the respective pistons are moving or are to be moved from their bottom dead center positions to their top dead center positions, and to simultaneously interconnect the outlet with the cylinders wherein the respective pistons are moving from their top dead center positions to their bottom dead center positions, a suitable nou-rotatable Valve plate is disposed in the housing cavity between the cylinder block and the inlet and outlet. The valve plate is formed with a pair of arcuately shaped openings. One of the openings formed in the valve plate is fluidly interconnected with the inlet and is so constructed and arranged to place the inlet in tluid communication with each cylinder during substantially the complete intake stroke of the respective piston. The other opening is iluidly interconnected with the outlet and is adapted to interconnect the outlet with each cylinder during substantially the complete discharge stroke of the respective piston.

In order to vary the displacement of a hydraulic apparatus of the previously described type without changing the speed of the operation thereof when acting as a pump or without changing the pressure value of the pressure uid when acting as a motor, i.e., to vary the actual amount of luid which is permitted to pass from the inlet to the outlet when the hydraulic apparatus is operating at a constant speed as a hydraulic pump or when operating with a constant pressure value of the pressure fluid when acting as a hydraulic motor, some means must be provided to vary the effective strokes of the pistons by varying the actual movement thereof or varying the actual amount of iluid displaced by the pistons from the inlet to the outlet without changing the actual movement of the pistons.

One means for varying the displacement of a hydraulic apparatus of the previously described type has been to vary the angular position of the axis of rotation of the rotatable member relative to the axis of rotation of the cylinder block by moving the rotatable member relative to the cylinder .block or the cylinder block relative to the rotatable member. However, in this prior known device, although the actual movement of each piston between its bottom dead center posi-tion and its top dead center position has been reduced in order to provide for variable displacement, complex structure must be provided in order to vary the angular position of the cylinder block relative to the rotatable member thereby increasing production and maintenance costs.

Another means for varying the displacement of a hydraulic apparatus of the previously described type has been designed which varies the time that the Valve plate permits fluid communication .between the inlet and the cylinders wherein the respective pistons are moving from their bottom dead center positions toward their top dead center positions. However, in this prior art design, when it is desired to have a partial displacement or zero displacement condition, each cylinder, during at least a portion of the intake stroke of the respective piston, is not interconnected With the inlet lwhereby movement of the respective piston creates a vacuum condition in its respective cylinder until the valve plate permits the inlet to be uidly interconnected therewith. Because a vacuum condition is created Within each cylinder before it is interconnected with the inlet, the resulting rush of uid from the inlet into the cylinder when the cylinder is eventually interconnected ,therewith tends to break down the surfaces of the valve plate and/or the cylinders, this rupture of the surfaces occurring by the well known adverse cavitation condition created and causing malfunctioning of the hydraulic apparatus.

Therefore, it has been found that a hydraulic apparatus of the previously described type can be produced with means for varying the displacement thereof without changing the angular position of the rota-table member relative to the cylinder block and without having'the cavitation disadvantage, and it is an object of this invention to provide such a hydraulic appara-tus.

It is, therefore, an object of this invention to provide an improved variable displacement hydraulic apparatus.

Another object of this invention is to provide a piston type hydraulic apparatus having means for varying the displacement thereof.

A further object of this invention is to provide a hydraulic apparatus of the piston type having means for interconnecting the inlet and outlet fwith a cylinder at different positions of the respective piston in order to vary the displacement of the hydraulic apparatus.

A more specific object of this invention is to provide a hydraulic apparatus comprising, a housing having a charnber and an inlet and an outlet leading respectively to and from the chamber, fluid'displacing means disposed in the chamber adapted to receive Viluid from the inlet and deliver the same out through the outlet upon movement of the fluid displacing means, a movable valve element disposed in the chamber between the iluid displacing means and the inlet and outlet and being adapted to interconnect the inlet and outlet with the fluid displacing means, and means for moving the valve element relative to the fluid displacing means to interconnect the inlet and outlet with the fluid displacing means at diierent positions of the uid displacing means to vary the displacement of the apparatus.

Other and more particular objects, advantages and uses of this invention will lbecome apparent from a reading of the following specification taken in connection with the accompanying drawings forming a part thereof and wherein:

FIGURE 1 illustrates, in an axial cross-sectional view, a hydraulic apparatus formed in accordance with the teachings of this invention.

FIGURE 2 illustrates, in a cross-sectional view, certain operating parts of the hydraulic apparatus illustrated in FIGURE l and is taken on line 2 2 thereof.

FIGURE 3 illustrates, in a partial cross-sectional View, certain other operating parts of the hydraulic vapparatus illustrated in FIGURE l andy is taken on line 3 3 thereof.

FIGURE 4 is across-sectional View of the hydraulic apparatus illustrated in FIGURE 1 and is taken on line 4 4 thereof.

FIGURES illustrates, .in a schematic view, a portion of the hydraulic apparatus illustrated in FIGURE 1.

FIGURE k6 illustrates, in a schematic view similar t0 FIGURE 2, certain operating parts of the hydraulic apparatus illustrated inFIGURE 1.

FIGURE 7 is a partial cross-sectional view similar to FIGURE 2 and illustrates particular operating positions of certain parts of the hydraulic apparatus illustrated in FIGURE 1.

FIGURE 8 illustrates, in a View similar to FIGURE 7, -other operating positions of the parts illustrated in FIG- URE ,7.

FIGURE 9 illustrates, in a partial cross-sectional view, other operating positions of the parts illustrated in FIG- URE 4.

Reference is now made to the accompanying drawings lwherein like reference letters and numerals are used throughout the various figures to designate like parts where appropriate, and particular reference is made to FIGURE l illustrating a hydraulic apparatus, generally indicated by the reference letter A, `formed in accordance with the teachings of Ithis invention and including a housing l10- comprising a plurality of housing sections 11 and 12 suitably secured together in aligned relation in a manner :well known in the art.

The housing section 11 has a flat end wall 13 interrupted by a stepped bore means 14 comprising a plurality of cylindrical bore sections 15, 16 and 17, the bore sections 15, 16 and 17 respectively having diameters substantially smaller than the preceding section and being disposed coaxially along an axis 1S of the stepped bore means 14. Another end wall 19 of the housing section 11 is interrupted by a stepped bore means20 comprising a plurality of bore sections-21, 22 and 23, the bore sections 21, 22 and 23 respectively having diameters substantially smaller than the preceding sections and being disposed coaxialiy along an axis 24 of the stepped bore means 2t). The axis 18 of the stepped bore means 14 angularly intersects the axis 24 of the stepped bore means 20, the stepped bore means 14 and 20 cooperating to `define a chamber B within the housing v1t). The chamber B is fluidly interconnected with the exterior ofthe housing 1G by a suitable drain port -25 formed in the housing section 11.

ri'he housing section -12 is provided with a substantially flat end wall v26 which is adapted to sealably a-but the at end wall 13 of the housing section 11 when the housing sections 11 and '12 aresecured together. The end wall 26 is adapted to close ot one end of the chamber B.

A cylindrical cylinder block 27 is disposed within the stepped bore means l-' of the cavity VB and is supported for rotation about the axis 18 by .bearing means 28, the bearing means 2S being disposed between a sleeve 29 telescopically disposed within the bore section :16 and the cylinder Ablock 27. The sleeve 2.9 is provided with an annular groove 36 at one end thereof adapted to cooperate Iwith the bore section 15 to provide an annular groove 311. A suitable sealing means 32 is disposed in the annular Vgroove 31 and is utilized to seal the housing sections 11 and 12 together.

The cylinder block 2.7 is provided with a tubular projection 33 extending from a hat side 34 thereof, the at side 3d being disposed substantially parallel to and spaced from another .flat side 35 of the cylinder block 27. A t lurality of cylinders 36 are formed in the cylinder block 27 and interconnect the iiat sides 34 and 35. One end 37 of each cylinder 36 is reduced and is adapted to cooperate with a rotatable valve plate 38 in a manner later to be described.

The valve plate 38 is disposed in the cavity B between the cylinder block 27 and the iiat end wall 26 of the housing section 12, the valve plate 38l having a pair of spaced opposed iiat surfaces 39 and 40 disposed respectively in sealing engagement with the at end wall 26 of the housing section 12 and the tlat side 35 of the cylinder block 27.

A plurality of pistons 41 each having an enlarged head portion 42 are disposed respectively in the cylinders 36. Each piston 41 has a substantially spherical end portion 43 secured Within a respective socket 44 `formed in one end of a rotatable memberV 45. The rotatable member 45 is disposed within the fbore means 20 of the housing section 11 and is supported forV rotation about the axis 24 by a plurality of bearing means 46 interposed between the ,rotatable member 45 and a sleeve 47 having a portion thereof telescopically received Within the bore section 22. The sleeve 47 is suitably secured to the housing section l11 by a plurality of bolts 43 passing through a plurality of apertures `49 formed in a flanged portion 50 of the sleeve member 47, the flanged portion 50 being telescopically received Within the bore section 2.11 of the housing section 11.

The rotatable member 4S has an end 51 thereof interrupted by a bore 52 which terminates within the rotatable member 45. The bore 52 of the rotatable member 45 is internally splined at 53 in order to be interconnected to an externally splined end 54 of a shaft 55 projecting from the end `19 of the housing 11). The shaft 55 provides a drive member when the apparatus A is utilized as a hydraulic pump and provides a power take off member when the apparatus A is utilized as a hydraulic motor.

The rotatable member 45 is provided with a substantially spherical end portion 56 adapted to be telescopically received within the tubular portion 33 or" the cylinder block 27. The spherical end portion 56 of the rotatable member 45 carries a plurality of pins 57 projecting radially therefrom and being respectively received within a plurality of slots 58 formed in the tubular portion 33 of the cylinder block 27, the pins 57 and slots 58 operatively interconnecting the rotatable member 45 and cylinder block 27 together. In this manner, rotational movement of the rotatable member 45 causes rotational movement of the cylinder block 27 through the driving relation of the pins 57 and the slots 53 formed in the tubular portion 33 of the cylinder block 27. Since the axis `24 of rotation of the rotatable member 45 is angularly disposed with respect to the axis 13 of rotation of the block 27, the spherical end `56 of the rotatable member 45 and the slots `58 of the block 27 permit relative movement between the block 27 and the rotatable member 45 to compensate `for this angular relation.

When the rotatable member 45 is rotated, each piston 41 carried by the rotatable member 45 is reciprocated relative to the block 27 Within the respective cylinder 36, the pistons 41 each moving from a bottom dead center position 59 as shown in FIGURE y3 to a top dead center position 60 upon 180 degrees of rotational movement of the rotatable member 45 and moving from a top dead center position 60 to a bottom `dead center position 59 upon a fur-ther rotational movement of 180 degrees of the rotatable member 45 because of the angular relation of the respective axes `1i? and 24 of rotation of the block 27 and member 45.

The valve plate 38 is provided with a pair of kidney shaped openings 61 and 62 respectively interconnecting the opposed sides 39 and 40 thereof (see FIGURES l, 4 and 9). The opening 61 in the valve plate 38 is uidly interconnected with an inlet 63 formed in the housing 10. The other opening 62 formed in the valve plate 3S is in uid communication with an outlet 64 formed in the housing 10. The inlet 63 interrupts the flat end wall 26 of the housing section 12 and defines a kidney shaped opening 63a adapted to cooperate with the valve plate inlet opening 61. Similarly, the outlet 64 interrupts the at end wall 26 of the housing section 12 and defines a kidney shaped opening 64a adapted to cooperate with the valve plate outlet opening 62.

The valve plate 38 is provided with a centrally disposed internally splined bore 65 adapted to receive a splined end 66 of a rotatable shaft 67 of a motor C later to be described. The valve plate 38, therefore, is mounted for rotational movement about an axis of rotation 68 which is disposed Icoincident with the axis 18 of rotation of the cylinder block 27.

As shown in FIGURE 4, the inlet opening 61 and the outlet opening 62 formed in the valve plate 38 are equally spaced on opposite sides of a plane 69 passing respectively through the points 59 and 60 where each piston 41 reaches its respective bottom dead center position 59 and its top dead center position 6i). The valve plate 3S is adapted to be rotated about the axis 63 in a counterclockwise direction from the position illustrated in FIG- URE 4 to the position illustrated in FIGURE 9 upon rotation of the shaft 67 in a manner later to be described. As illustrated in FIGURE 9, the inlet opening 61 and the outlet opening 62 are each bisected by the plane 69, i.e., one half of each opening 61 and 62 is disposed respectively ou opposite sides of the plane 69. As the valve plate 38 is rotated 90 degrees from the position illustrated 0 in FIGURE 4 to the position illustrated in FIGURE 9, the inlet opening 61 remains in fluid communication with the inlet 63 through the cooperation of the kidney shaped opening 63a and the inlet opening 61. Similarly, the outlet opening 62 remains in fluid communication with the outlet 64 through the cooperation of the kidney shaped opening 64a and the outlet opening 62.

The operation of the hydraulic apparatus A, as set forth above, will now be described. Assuming that the hydraulic apparatus A is -operating as a hydraulic pump and the valve plate 3S is in the position illustrated in FIGURE 4, a suitable power source (not shown) is interconnected with the shaft 55 and causes rotation thereof in a clockwise direction as viewed in FIGURE 3. Since each piston 41 is carried by the rotatable member 45, and, therefore, is rotated therewith, each piston is reciprocated within the respective cylinder 36 as the piston 41 is rotated from its bottom dead center position 59, to its top dead center position 60, and back to its bottom dead center position 59.

When each piston is at its bottom dead center position 59, the opening 37 of the respective cylinder 36 comes into iiuid communication with the inlet opening 61 in the valve plate 38. As each piston 41 is rotated from its bottom dead center position 59 to its top dead center position 60, the respective piston 41 draws fluid from the inlet 63 into the respective cylinder 36 as the cylinder 36 remains in fluid communication with the inlet opening 61 throughout substantially the entire intake stroke of the piston 41. As each piston 41 is rotated to its top dead center position 60, the respective cylinder 36 moves out of fluid communication with the inlet opening 59 whereby the uid drawn into the cylinder 36 is completely trapped therein. Upon further movement of each piston 41 in a clockwise direction, as viewed in FIGURE 3, the respective piston 41 begins to move toward its bottom dead center 59. As each piston 41 is rotated past its top dead center position 60, the respective cylinder 36 comes into tiuid communication with the outlet opening 62 formed in the valve plate 38 whereby movement of the piston from its top dead center position 6@ to its bottom dead center position 59 expels the fluid previously received Within the respective cylinder 36 out through the outlet 64. As long as the valve plate 38 remains in the position illustrated in FIGURE 4, the inlet 63 remains in uid communication with each cylinder 36 during substantially the entire intake stroke of the respective piston 41 and the outlet 64 remains in fluid communication with the respective cylinder 36 during substantially the entire discharge stroke of the respective piston 41 whereby the apparatus A is operating at its maximum displacement condition for a particular speed of rotation of the drive shaft 55 as the entire amount of fluid drawn into each cylinder 36 from the inlet 63 is delivered to the outlet 64.

When the valve plate 38 has been rotated to the position illustrated in FIGURE 9, by any suitable means, the hydraulic apparatus A will be operating at its zero displacement condition in the following manner. As previously described, when each piston 41 is rotated and is moved past its bottom dead center position 59, the respective piston 41 begins its intake stroke, drawing fluid into the respective cylinder 36. However, as shown in FIG- URE 9, when each cylinder 36 is rotated counterclockwise past point 59, the respective piston draws liuid therein from the outlet 64 as the outlet opening 62 is in uid communication with the respective cylinder 36 during the lirst half of the intake stroke of the respective piston 41. During the last half of the intake stroke of each piston 41, the respective cylinder 36 comes into communication with the inlet opening 61 whereby the respective piston 41 draws half or" the fluid filling the respective cylinder 36 from the outlet 64 and the remaining half from the inlet 63. As each piston moves past its top dead center position 60, the respective cylinder 36 is disposed in uid communication with the inlet opening `61 of the valve plate during half of the discharge stroke of the respective piston 41 whereby the respective piston 41 expels half of the uid previously drawn into. the cylinder 36 back to the inlet 63. During the last half of the discharge stroke of the respective piston 41',` the respective cylinder 36 cornes into fluid communication with the outlet opening 62 of the valve plate 38 whereby the remaining fluid in the cylinder 36 is expelled to the outlet 64.' Therefore, since half of the fluid received within each cylinder 36 is drawn from the outlet 64 and the other half is drawn from the inlet 63, and since half the fluid received'in each cylinder 36 is discharged to the inlet 63 and the other half to the outlet 64, the net displacement of the hydraulic apparatus is zero, i.e., the actual amount of fluid delivered from the inlet 63 to the outlet 64 is zero.

As the valve plate 3S is rotated from the position illustrated in FIGURE 4 providing maximum delivery toward the position illustrated in FIGURE 9 providing zero delivery, the delivery of the hydraulic apparatus A is progressively and Vinfinitely reduced as each cylinder 36 is placed in fluid communication with the outlet opening 62 during a greater portion of the intake stroke and with the inlet opening 61 during a greater portion of the discharge stroke until zero delivery is reached. Conversely, when the valve plate 38 is moved from the position illustrated in FIGURE 9 toward the position illustrated in FIGURE 4, the delivery of the hydraulic apparatus A will be progressively and infinitely increased as each cylinder 36 is placed in fluid communication with the inlet opening 61 during a greater portion of the intake stroke and with the outlet opening 62 during a greater portion ofthe discharge stroke until maximum delivery is reached. Therefore, when the valve plate 38 is disposed in any position between its maximum and zero delivery positions the hydraulic apparatusA will be operating at a partial delivery condition. By changing the delivery fromA the hydraulic apparatus A, as described above, the overall displacement by the apparatus A is varied.

Although theqoperation of the hydraulic apparatus A- has been described when operating as a hydraulic pump, it is to be understood that the operation thereof occurs in substantially the same manner when operating as a hydraulic motor, the valve plate 38 regulating the amount of pressure fluid delivered to each cylinder 36 and thus the power output` of the apparatus A. The valve plate 38,l

therefore, regulates the intake of the hydraulic apparatus A when operating as a hydraulic motor, i.e., varies the actual amount of fluid that passes from the inlet 63 to the outlet 64.

It is to be understood that many means could be provided for selectively varying the position of the valve plate 38 to provide for variable delivery by the hydraulic apparatus A; One such means will now be described.

As previously stated, the valve plate 38 is rotatably mounted on a rotatable shaft 67 of a motor C, the motor C being disposed within a bore 70 formed in the housing 10. The shaft 67 has an enlarged cylindrical portion 71 telescopically received within a stationary tubular member 72 disposed within .the bore 7d. The tubular lmember 72 has a flanged portion 73 at one end thereof, the anged portion 73 having a substantially iiat surface 74 sealably abutting a shoulder 75 Vformed at the juncture of the bore 70 with a smaller counter bore 76 formed in the housing 10. The counter bore 76 is coaxially disposed with respect to the bore '76 and terminates within the housing section 12 defining an end wall 77 therein. A washer-like member 78 is disposed in the counter bore 761 and surrounds the cylindrical portion 71 of the shaft 67. The washer-like member 78 is provided with a pair of opposed at sides 79 and 80, the side 80 being disposed in sealing relation with the end wall 77 and the side 79 being disposed spaced from the flat surface 74 of the tubular member 72. The flat surfaces 74 and 79 of the respective members 72 and 78 cooperate together with the shaft portion 71 and the housing 10 to define a sealed annular cavity 81.

A slot S2 is formed radially through the cylindrical portion 71 of the shaft 67 and is adapted to receive a vane 83, the vane y8?) projecting radially on each side of the cylindrical portion 71 to define a pair of fins or vanes 84 and 85 disposed in the annular cavity 81. An annular member 36 is disposed within the annular cavity 81 and has an external peripheral surface 87 disposed in sealing engagement with the internal peripheral surface of the housing 1G, the internal peripheral surface of the housing 11B being defined by the counter bore 76. An internal peripheral surface 83 of the annular member 86 is adapted to be sealably engaged by the fins or vanes 84 and 8S carriedby the shaft 67.

The annular member 86 is provided with an annular groove S9 interrupting the external peripheral surface 87 thereof, the annular groove S9 being disposed in fluid communication with a passage 90 formed in the housing 1t) and leading to a control valve D later to be described. The annular member S6 carries a pair of stop means 91 and 92 projecting from ange 73.` The stop means 91 and 92 have arcuately shaped ends 93 adapted to be disposed in sealing engagement with the cylindrical portion 71 of the shaft 65. The stop members 91 and 92 respectively cooperate with the fins or vanes 84 and 8S to define a pair of chambers 94 and a pair yof chambers 95, the

chambers 95 being respectively disposedV in fluid cornmunication with the bore 70 by passages 96 formed in the flanged portion 73 of the tubular member 72.

A coiled torsional spring 97 is disposed within the bore 7! and has a radially inwardly projecting end 98 received in a slot 99 formed in the tubular member 72 and another radially inwardly projecting end 169 thereof projecting through a slot 191 formed in the sleeve member 72 and received within a slot 102 formed in the cylindrical mem- 'ber 71 of the shaft 67.` Since the tubular member 72 is fixed relative to the housing 1@ by a pin 103 projecting through the housing section 12 and being received in a slot 104 `formed in the flanged portion 73 thereof, the torsional spring 97 tends to rotate the shaft 67 in a clockwise -direction when looking at FIGURE 2 whereby the fins S4 and 85 are respectively disposed in engagement with the stop means 91 and 92 and the valve plate 38 is disposed in the maximum displacement position illustrated in FIGURE 4.

The chambers 94 are respectively placed in fluid communication with the annular groove 89 formed in the annular member 36 by ports 105 formed in the annular member S6, the ports 165 thereby fluidly interconnecting the chambers 94 with the passage 90 formed in the housing 1li and leading to the control valve D.

The control valve D includes a stepped ybore means 106 formed in the housing 10, the bore means 106 having a plurality of cylindrical bore sections 107, 108,' and 109; A sleeve member 110 is disposed within the bore section 169 and has a flanged end portion 111 disposed within the bore section 168. The sleeve 110 is maintained within the bore means 166 by a tubular plug member 112 threadedly received within the bore section 167 and disposed in engagement with the flanged portion 111 of the sleeve 110. The sleeve 116 is provided with a central bore 113 passing therethrough and is adapted to telescopically receive a cylindrical valve member 114 therein. The sleeve 11G is provided with a pair of spaced annular grooves 115and 116, the annular groove 115 being disposed in fluid communication with the passage 96 leading to the motor C and the annular groove 116 being disposed in fluid communication with a passage 117 formed in the housing section 12 and leading to .the .bore 70. The annular groove 115 is, in turn, placed in fluid communication with the bore 113 formed in the sleeve 11G by a plurality of ports 118. Similarly, the annular groove 116 is placed in iluid communication with the bore 113 by a plurality of ports 119.

The valve member 114, telescopically received within the bore 113 or the sleeve 110, is disposed in sealing engagement therewith but is adapted to be axially movable relative thereto. The movable valve member 114 is provided with a pair of spaced annular grooves 120 and y121 which deline a sealing land portion 122 therebetween. The land 122 is of sufficient length to completely seal S the ports 118 from the annular grooves 120 and 121 when the valve member 114 is disposed in the position illustrated in FIGURE 2. The valve member 114 is provided with a pair of ends 123 and 124, the end 124 being interrupted by a bore 125 which terminates within the member 114 and communicates with a port disposed within land 122 in order to convey intermediate uid pressure to the inside of plug member 112. A pin 126 is disposed within the bore 125 of the member 1.14 and is carried by a cradle member 127 disposed within the tubular member 112. A compression spring 128 is interposed between the plug member 112 and the cradle member 127 and tends to urge the member 114 to the right as viewed in FIGURE 2.

The outlet 64 is interconnected with the end of the bore section 109 by a passage 129 yformed in the housing 10. In this manner, pressure iluid Within the outlet 64 is adapted to act on the end 123 of the member 114 and tends to move the member 114 to the left, as viewed in FIGURE 2, in opposition to the combined force of the compression spring 128 and the force of the intermediate uid pressure acting on the end 124 of valve member 114. The -force of the compression spring 128 can be selectively predetermined by adjusting the position of the plug member 112 relative to the housing 10 in a manner well known in the art.

The bore 70 of the motor C is uidly interconnected with the inlet 63 by a passage 130.

The control valve D and motor C cooperate with the valve plate 3S of the hydraulic apparatus A to vary the displacement of the apparatus A when operating as a hydraulic pump in accordance With the pressure value of the pressure uid delivered to the outlet 64 and acting against the end 123 of the control valve member 114. -In this manner, the hydraulic apparatus A will be prevented from delivering pressure fluid to the outlet 64 above a predetermined pressure value, the predetermined pressure value being determined by the particular compression setting of the spring 128 of the control valve D.

The operation of the hydraulic apparatus A utilizing the control valve D and motor C will now be described.V

Assuming that the hydraulic apparatus A is operating as a hydraulic pump and that it is desired that the pressure value of the pressure iluid delivered to the outlet 64 thereby will not exceed a predetermined pressure value, such as 3,000 p.s.i., the compression force of the spring 12S is set accordingly. Upon initial rotation of the drive shaft 55 by a suitable power source (not shown) driving the shaft at a constant speed, the valve plate 38 will be maintained in the position illustrated in FIGURE 4 providing Ifor maximum displacement of the hydraulic apparatus A by the torsional spring 97 in the manner previously described. As the hydraulic pump A receives uid from the inlet 63 and delivers the same out through the outlet 64, the outlet 64 being restricted in a manner well known in the art so that the iluid delivered thereto is placed under pressure, the pressure value of the pressure uid in the outlet 64 increases. As long as the pressure value of the pressure tiuid in the outlet 64 remains below 3,000 p.s.i., the control valve member 114 is moved by the force of the spring 12S to right from the position illustrated in FIGURE 2 preventing any iluid communication between the outlet 64 and the motor C and placing the passages 90 and 117 in uid communication by the annular groove 121 overlapping the ports 118 and 119.

When the pressure value of the pressure fluid delivered to the outlet 64 reaches 3,000 p.s.i., the valve member 114 is moved to the left to the position illustrated in FIGURE 10 2 whereby fluid communication between the outlet 64 and motor C is still prevented by the land 122 of the valve member 114. However, when the valve member is placed in the position illustrated in FIGURE 2, fluid communication is now prevented between the passages and 117 and thus between the chambers and the inlet 63.

If the pressure value of the pressure liu-id delivered to the outlet 64 increases to a pressure value greater than :3,000 p.s.i., the force thereof acting against the end 123 of the valve member 114 together with the force of the intermediate Huid pressure acting on the end 124 of valve member 114 causes movement of the valve member 114 to the left in opposition to the force of the spring 128 thereby placing the ports 118 in uid communication with the outlet 64. Since the annular groove formed in the end of the member 114 permits throttling of the tluid from the outlet 64 into the ports 118, an intermediate pressure fluid is created by the control valve D which passes to the ports 113. As shown in FIGURES 5 and 6, the intermediate pressure is communicated to the chambers 94 of the motor C by the passage 90, the annular groove 39, and ports 105. The force of the intermediate pressure delivered to the chambers 94 respectively acts against the ns 84 and S5 in opposition to the torsional force of the spring 97 and cause counterclockwise rotation of the shaft 67 as viewed in FIGURE 2. Counterclockwise rotation of the shaft 67 by the force of the intermediate pressure conveyed to the chambers 94 by the control valve D causes counterclockwise rotation of the valve plate 38 as viewed in FIGURE 4, from its maximum displacement position toward its zero displacement position. Movement of the valve plate 38 past the position illustrated in FIG-URE 9 providing zero displacement is prevented by the fins 34 and 85 abutting the respective stop means 92 and 91 (see FIGURE 8).

As previously described, when the valve plate is rotated from the position illustrated in FIGURE 4 toward the position illustrated in FIGURE 9, the displacement of the hydraulic apparatus A is decreased. Since the amount of uid displaced by the hydraulic apparatus A from the inlet 63 to the outlet 64 is decreased, the pressure value of the pressure fluid in the outlet 64 is correspondingly decreased. When the pressure value of the pressure Huid in the outlet 64 drops to 3,000 p.s.i., the spring 128 `acting in concert with the force of the intermediate uid pressure acting on the end 124 of Valve member 1.14 returns the valve member 114 to the position illustrated in FIGURE 2 thereby preventing further communication between the outlet 64 and the chambers 94 of the motor C. Since the fluid is now trapped within the chambers 94 by the control valve D and is noncompressible, the spring 97 cannot return the fins 84 and 85 against the respective stop means 91 and 92 (See FIG- URE 7). Therefore, the valve plate 38 remains in its particular operating position providing for partial displacement of the hydraulic apparatus A.

`If the pressure value of the pressure fluid delivered to the outlet 64, when the valve plate 33 is in a partial displacement position, should fall below 3,000 p.s.i., the spring 12S and the intermediate pressure acting on the end of valve member 114 will cause movement of the valve member 114 to the right from the position illustrated in FIGURE 2 thereby permitting fluid communication between the ports 118 and 119 through the annular groove 121. When the ports 118 and 119 are fluidly interconnected, the iluid within the chambers 94 is permit-ted to pass out through the passage 117 of the control valve D into the bore 70 of the motor C, and thus from the bore 70 to the inlet l63 by means of the passage 130. Since the chambers 94 are now vented to the inlet 63, the force of the torsional spring 97 causes rotation of the shaft 67 in a clockwise direction as viewed in FIGURE 2 effecting an increase in the displacement of the apparatus A until the pressure value in the outlet 64 reaches 3,000 p.s.i. whereby the control valve prevents further corn- 1 1 munication between the chambers 94 and the inlet 63 o1' the tins 84 and 85 engage the stop means 91 and 92. If the ns 84 and 8S are returned against the stop 91 and 92, the valve plate 38 will be in the position illustrated in FIGURE 4 and thus provide for maximum displacement of the hydraulic apparatus A.

Therefore, it can be seen that theV control valve D will tend to maintain the pressure value of the pressure fluidV delivered to the outlet 62 by the hydraulic apparatus A at a predetermined selected pressure value, the control valve D and motor C cooperating to eeet rotation of the valve plate 38 between the maximum and minimum displacement positions in order to cause the hydraulic apparatus A to deiiver pressure fluid at the predetermined selected pressure value.

It can be seen that there has been described an improved hydraulic apparatus having means for varying the displacement thereof without changing the actual movement of the pistons or subjecting the apparatus to adverse cavitation conditions.

While this invention has been disclosed in connection with a certain specific embodiment thereof,;it is-to be understood that this is by way of example rather than limitation, and it is intended that the invention be dened by the appended claims.

What is claimed is:

1. A hydraulic apparatus comprising: a housing having a chamber and an inlet and an outlet leading respectively to and from said chamber; a block disposed in said chamber and having a cylinder formed therein; a piston disposed in said cylinder, said piston being adapted to be reciprocated relative to said block in order to provide an intake stroke and a discharge stroke; a movable valve plate disposed in said chamber between said block and said inlet and outlet and being adapted to interconnect said cylinder with said inlet and outlet; and means for rmoving said valve plate relative to said block to interconnect said cylinder with said inlet during at least a portion of said discharge stroke and with said outlet during at least a portion of said intake stroke to vary the displacement'of said apparatus, said last-named means including a motor interconnected with said valve plate and comprising means dening a bore in said housing, a rotatable shaft disposed in said bore and being interconnected with said valve plate, biasing means operatively interconnected with said shaft and tending to maintain said valve plate in a predetermined rotational position relative to said housing providing for maximum displacement of said apparatus, means defining a motive surface on said shaft, and valve means for selectively applying and disapplyingpressure uid against said motive surface whereby the force of saidV fluid acting against said motive surface rotates said valve plate from said predetermined position in opposition to said biasing means to decrease the displacement of said apparatus.

2. A hydraulic apparatus comprising: a housing having a chamber and an inlet and an outlet leading respectively to and from said chamber; a block disposed in said cham ber and having a plurality of cylinders formed therein; a plurality of pistons disposed respectively in said cylinders, said pistons each being adapted to be reciprocated relative to said block in orderto provide an intake stroke and a discharge stroke; aA movable valve plate disposed in said chamber` between said block and said inlet and outlet and being adapted to interconnect said cylinders with said inlet and outlet; and means for moving said valve plate relative to said block to interconnect each cylinder with said inlet during at least a portion of the discharge stroke thereof and with said outlet during at least a portion of the intake stroke thereof to vary the displacement of said apparatus, said last-named means including a motor interconnected with said valve plate and comprising means dening a bore in said housing, a rotatable shaft disposed in said bore and being interconnected with said valve plate, biasing means operatively interconnected with said .shaft and tending to maintain said valve plate in a predetermined rotational position relative to said housing providing for maximum displacement of said apparatus, means defining a motive surface on said shaft, and Valve means for selectively applying and disapplying pressure uid against said motive surface whereby the force of said uid acting against said motive surface rotates said valve plate from said predetermined position in opposition to saidlbiasing means to decrease the displacement of said apparatus.

References Cited by the Examiner UNITED STATES PATENTS 1,466,092 8/ 23 Egersdorfer 103-162 2,164,876 7/ 39 Horlacher 121--99 2,313,407 3/43 Vickers et al. 103-162 `2,364,301 12/44 MacNeil 103-162 2,546,583 3/51 Born 103--162 2,642,809 6/53 Born et al. 103-162 ,2,695,598 11/54 Strang 121--99 2,847,938 8/58 Gondek 103--162 FOREGN PATENTS 794,288 4/58 Great Britain.

LAURENCE V. EFNER, Primary Examiner.

JOSEPH H. BRANSON, JR., Examiner. 

1. A HYDRAULIC APPARATUS COMPRISING: A HOUSING HAVING A CHAMBER AND AN INLET AND AN OUTLET LEADING RESPECTIVELY TO AND FROM SAID CHAMBER; A BLOCK DISPOSED IN SAID CHAMBER AND HAVING A CYLINDER FORMED THEREIN; A PISTON DISPOSED IN SAID CYLINDER, SAID PISTON BEING ADAPTED TO BE RECIPROCATED RELATIVE TO SAID BLOCK IN ORDER TO PROVIDE AN INTAKE STROKE AND A DISCHARGE STROKE; A MOVABLE VALVE PLATE DISPOSED IN SAID CHAMBER BETWEEN SAID BLOCK AND SAID INLET AND OUTLET AND BEING ADAPTED TO INTERCONNECT SAID CYLINDER WITH SAID INLET AND OUTLET; AND MEANS FOR MOVING SAID VALVE PLATE RELATIVE TO SAID BLOCK TO INTERCONNECT SAID CYLINDER WITH SAID INLET DURING AT LEAST A PORTION OF SAID DISCHARGE STROKE AND WITH SAID OUTLET DURING AT LEAST A PORTION OF SAID INTAKE STROKE TO VARY THE DISPLACEMENT OF SAID APPARATUS, SAID LAST-NAMED MEANS INCLUDING A MOTOR INTERCONNECTED WITH SAID VALVE PLATE AND COMPRISING MEANS 